1. Field of the Invention
The present invention relates to an electrophotographic apparatus, such as an electrophotographic printer or copier, for making and recording an image, and more particularly, it relates to a compact electrophotographic recording apparatus in which a face-down, correct-order stack of recorded cut sheets can be produced.
2. Description of the Related Art
In an electrophotographic printer, a light emitting diode (LED) array changes image data, stored in a memory in a page format, into light patterns. These light patterns are used to form a latent image on a photoconductive drum by an array of LED's. A photoconductive drum is then rotated and a developing unit distributes charged small particles, called toner, which consist of carbon and resin, onto the photoconductive drum while the drum is rotated. The toner adheres to areas on the drum which do not have a charge, i.e., develops a latent image and thus produces a visible image on the drum. Paper fed from a hopper is given a charge having a polarity opposite to that of the toner by a corona discharger and brought into contact with the drum. Thus, the toner is transferred to the paper as a visible image. The toner is then melted by a heat roller to form a permanent image on the paper while the paper is passing through the heat roller, and the resultant printed paper is sent to a stacker.
Various compact electrophotographic printers using a toner, which provide a high quality and stable printing of cut sheets, are generally known. However in these conventional compact electrophotographic printers, the printed papers are stacked in reverse order. Namely, in the stack of printed papers, the printed surfaces of which face upwards the first page is located at the bottom of the stack and the last page is located at the top. This requires a time-wasting rearrangement by a user of the order of the pages of printed-out paper or requires the addition of a paper tipping device, usually provided downstream of a fixing unit, to reverse the printed surface of the paper, making the printer large, expensive and complex.
Compact electrophotographic printers in which a correctly ordered stack can be realized without a paper tipping device are also known. In the known electrophotographic printers of this type, the toner forming an image on the photoconductive drum is transferred to the undersurface of the paper to be printed by a transfer unit. Thus the printed papers are sent to a stacker and are stacked therein in a face-down stack.
In this kind of face-down stack compact type printer, the problems arise of a stable feed of the paper along the paper path without a paper jam and a reliable separation of the paper from the photoconductive drum. A complete separation of the paper from the photoconductive drum becomes more difficult when the diameter of the drum is increased. The problem of a stable feed of the paper mainly arises because the paper must be held from the upper side thereof, as the underside of the paper has unfixed toner formed thereon. This means that the paper cannot be slid on and along a paper guide. One solution to the paper hold problem is to utilize a vacuum unit by which the paper can be lifted from above. However, this vacuum suction mechanism makes the printer more expensive, more complex, and larger and thus inhibits the realization of a compact, simple and inexpensive printer. In addition, in the conventional face-down stack printer, the paper tends to collide with a heat roller of the fixing unit, resulting in a paper jam.